1. Field of the Invention
The present invention generally relates to an apparatus and method for a Bluetooth receiver, and more particularly for relating to simplified acquisition apparatus and method for a Bluetooth receiver, receiving a Bluetooth basic data rate (BDR) or enhanced data rate (EDR) packet. It features a simplified acquisition circuit implementation with a 1-bit correlator hardware shared by access code and EDR synchronization sequence correlation computations.
2. Brief Description of the Related Art
In a wireless communication system such as Bluetooth [Specification of the Bluetooth System, 2.0+EDR, 4 Nov. 2004], packet acquisition is the first step toward a successful packet reception. A lost packet, on the other hand, can cause degraded wireless link quality. A Bluetooth BDR/EDR packet contains a known access code of 68 or 72 bits (FIG. 1). An access code correlator is typically used in a Bluetooth receiver to detect the arrival of a Bluetooth packet and in the meantime, determines the coarse timing of the received packet. This is also known as the “packet acquisition” process. Since a Bluetooth device is typically battery-based, the current consumption of a Bluetooth device is extremely important.
A simplified Bluetooth acquisition circuit implementation with robust Bluetooth packet acquisition is, therefore, desired. An access code correlator, dependent on its sample resolution, can become a dominant (in circuit complexity and hence current consumption) part of a Bluetooth receiver. Since Gaussian frequency shift keying (GFSK) modulation is used for access code transmission, the simplest correlator implementation uses a 1-bit representation of the frequency deviation, derived from the received waveform samples, for its correlation computation. As a comparison, if an N-bit correlator is implemented, the amount of data buffered will be N times greater. As the packet detection is typically based on the computed correlation peak exceeding a certain threshold value, the trade-off is the accuracy in the correlation peak evaluation. And the Bluetooth acquisition circuit would cause degraded timing estimation, and in the worst case, a lost packet.